Patterning method, patterning apparatus, and method for manufacturing semiconductor device

ABSTRACT

A patterning method includes supplying an imprint material made of a dielectric in an uncured state onto a workpiece, producing a potential difference between the workpiece and a conductive pattern portion of a template opposed to the workpiece to induce dielectric polarization in the imprint material before curing the imprint material, bringing the pattern portion into contact with the imprint material in the uncured state, curing the imprint material with the pattern portion brought into contact with the imprint material, and stripping the template from the imprint material after curing the imprint material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-110295, filed on Apr. 30, 2009; the entire contents of which are incorporated herein by reference.

BACKGROUND

Embodiments of this invention relate generally to a patterning method, a patterning apparatus, and a method for manufacturing a semiconductor device.

Recently, imprint technology has been introduced into patterning of semiconductor devices. For instance, JP-A-2008-068612 proposes an imprint technique using light irradiation. In this technique, a template with an indentation pattern is pressed against a substrate coated with an imprint material made of ultraviolet-curable resin, and irradiated with ultraviolet radiation to cure the imprint material so that the pattern formed in the template is transferred at equal magnification to the imprint material.

The process of pressing the template against the uncured imprint material requires substantial time to gaplessly fill up the template pattern with the imprint material. This is one of the factors interfering with the increase of throughput in patterning using imprint technology.

SUMMARY

According to an aspect of the invention, there is provided a patterning method including: supplying an imprint material made of a dielectric in an uncured state onto a workpiece; producing a potential difference between the workpiece and a conductive pattern portion of a template opposed to the workpiece to induce dielectric polarization in the imprint material before curing the imprint material; bringing the pattern portion into contact with the imprint material in the uncured state; curing the imprint material with the pattern portion brought into contact with the imprint material; and stripping the template from the imprint material after curing the imprint material.

According to another aspect of the invention, there is provided a patterning apparatus including: a workpiece holder capable of holding a workpiece; a template holder capable of holding a template including a conductive pattern portion; a contact probe connected to a power supply and being capable of moving relative to the pattern portion to come into contact therewith; a moving mechanism configured to cause the workpiece holder and the template holder to move close to each other to bring the pattern portion into contact with an imprint material made of a dielectric in an uncured state supplied onto the workpiece, and to cause the workpiece holder and the template holder to move away from each other after the imprint material is cured; and a controller configured to apply a voltage to the pattern portion through the contact probe in contact with the pattern portion before the imprint material is cured.

According to still another aspect of the invention, there is provided a method for manufacturing a semiconductor device, including: supplying an imprint material made of a dielectric in an uncured state onto a workpiece; producing a potential difference between the workpiece and a conductive pattern portion of a template opposed to the workpiece to induce dielectric polarization in the imprint material before curing the imprint material; bringing the pattern portion into contact with the imprint material in the uncured state; curing the imprint material with the pattern portion brought into contact with the imprint material; stripping the template from the imprint material after curing the imprint material; and processing the workpiece by using the imprint material from which the template has been stripped as a mask.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a patterning apparatus according to an embodiment of the invention;

FIGS. 2A to 2E are schematic views showing a method for manufacturing a template used for patterning according to the embodiment of the invention; and

FIGS. 3A to 4C are schematic views showing a patterning method according to the embodiment of the invention.

DETAILED DESCRIPTION

The process of pressing the template against the uncured imprint material often requires a time period of approximately 10 seconds to gaplessly fill up the depression of the indentation pattern in the template with the imprint material. Typically, the patterned surface of the template is coated with a mold release agent so that the cured imprint material can be cleanly demolded from the template. Here, poor wettability between the mold release agent and the imprint material is considered to be one of the factors interfering with rapid fill-up of the pattern depression with the imprint material.

If the amount of mold release agent is decreased, the time required for demolding must be prolonged. That is, unless the template is slowly stripped from the imprint material, the imprint material is not cleanly stripped from the pattern portion of the template and may cause defects in the imprint material pattern.

In another technique proposed previously, a piezoelectric thin-film element is formed inside the imprinting mold and contracted to facilitate demolding. However, this is just an effort to improve mold releasability by energizing and driving the piezoelectric thin-film element after curing the imprint material, and not to facilitate rapid fill-up of the template pattern with the uncured imprint material. Furthermore, to ensure the transfer accuracy of fine patterns requiring high accuracy, such as semiconductor device patterns in particular, it is desired that the template pattern portion be made of a material with high mechanical strength, free from expansion and contraction.

Embodiments of the invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a patterning apparatus according to an embodiment of the invention.

The patterning apparatus according to this embodiment primarily includes a holder 4 for oppositely holding a workpiece to be patterned and a template, a moving mechanism 2 for the holder 4, a contact probe 7 to be in contact with a conductive film, described later, including the pattern portion of the template, a power supply 3 for supplying voltage to the contact probe 7, and a controller 1 for controlling the operation of the moving mechanism 2 and the power supply 3.

The holder 4 includes a workpiece holder 5 for holding the workpiece and a template holder 6 for holding the template. The moving mechanism 2 causes the workpiece holder 5 and the template holder 6 oppositely disposed as described later to relatively move close to or away from each other.

Next, a patterning method according to the embodiment of the invention is described. First, a method for manufacturing a template is described with reference to FIG. 2.

In this embodiment, as shown in FIG. 2E, the template 10 has a structure in which a conductive pattern portion 15 is formed on a substrate 11 illustratively made of quartz.

First, as shown in FIG. 2A, a conductive film 12 is formed on the substrate 11 made of quartz. The conductive film 12 is illustratively a DLC (diamond-like carbon) film provided with conductivity by impurity doping. Furthermore, a chromium (Cr) film 13 is formed on the conductive film 12, and an electron beam resist film 14 is formed further thereon.

Next, the resist film 14 is subjected to electron beam lithography, and then developed. Thus, as shown in FIG. 2B, the resist film 14 is patterned.

Next, the patterned resist film 14 is used as a mask to selectively remove the chromium film 13 by dry etching. Thus, as shown in FIG. 2C, the chromium film 13 is patterned. Subsequently, the patterned chromium film 13 is used as a mask to selectively remove the conductive film 12 by dry etching. Thus, as shown in FIG. 2D, the conductive film 12 is patterned.

If the etching selection ratio of the resist film 14 with respect to the conductive film 12 is relatively high, the resist film 14 may be formed directly on the conductive film 12 and patterned, and the patterned resist film 14 may be used as a mask to pattern the conductive film 12.

After the process of FIG. 2D, the chromium film 13 left on the conductive film 12 is removed. Thus, the template 10 shown in FIG. 2E is obtained. The pattern portion 15 with an indentation pattern formed in the conductive film 12 is provided at the center along the surface of the substrate 11.

In the figure, the substrate 11 has a uniform thickness. However, typically, it is configured to have a so-called mesa structure in which the outer portion is thinner than the center portion including the pattern portion 15, which thus protrudes from the other portion. This can bring only the pattern portion 15 into contact with the imprint material and avoid contact in the area more than necessary between the template 10 and the imprint material, thereby facilitating demolding.

Next, a patterning method using the aforementioned template 10 is described with reference to FIGS. 3 and 4.

As shown in FIG. 3A, the workpiece 20 is held on the workpiece holder 5, and the template 10 is held on the template holder 6 oppositely provided above the workpiece holder 5. The workpiece holder 5 illustratively includes a vacuum chuck mechanism. Likewise, the template holder 6 also includes a vacuum chuck mechanism. It is noted that in FIG. 3B and the subsequent figures, the workpiece holder 5 and the template holder 6 are not shown.

The workpiece 20 is illustratively a silicon or other semiconductor wafer, and held on the workpiece holder 5 with the surface to be processed facing upward. An imprint material 21 is supplied onto the surface to be processed of the workpiece 20. The imprint material 21 is a dielectric, such as an ultraviolet-curable resin. The imprint material 21 is supplied onto the workpiece 20 as an uncured liquid or paste.

The template 10 is held on the template holder 6 in a state in which the pattern portion 15 formed in its conductive film 12 is opposed to the imprint material 21 supplied onto the workpiece 20.

In the state shown in FIG. 3A, under the control of the controller 1 shown in FIG. 1, the moving mechanism 2 causes the template holder 6 and the workpiece holder 5 to relatively move close to each other. Here, with the workpiece holder 5 left at rest, the template holder 6 is moved down. Naturally, the workpiece holder 5 may be moved up with the template holder 6 left at rest, or both of them may be moved close to each other.

When the template 10 is moved close to the imprint material 21, as shown in FIG. 3B, a positive voltage is applied to the conductive pattern portion 15 of the template 10.

Specifically, the contact probe 7 connected to the power supply 3 is brought into contact with the surface of the conductive film 12 including the pattern portion 15 to apply a voltage to the pattern portion 15.

For instance, the contact probe 7 is cantilevered on a contact probe holder 8. The contact probe holder 8 can be moved with respect to the conductive film 12 by a contact probe moving mechanism, not shown. The contact probe 7 is in pressure contact with the conductive film 12 and electrically connected to the pattern portion 15 in an opposing space between the template 10 outside the pattern portion 15 and the workpiece 20. Alternatively, the contact probe 7 may be brought into contact with the side surface of the conductive film 12 exposed to the side surface of the template 10.

The workpiece 20 is grounded. Here, the workpiece 20 may be directly grounded, or the workpiece holder 5 may be directly grounded so that the workpiece 20 is grounded through the workpiece holder 5.

The downward movement of the template 10 causes the pattern portion 15 of the template 10 to be brought into contact with and pressed against the uncured imprint material 21 as shown in FIG. 3C. Here, a positive voltage is applied to the pattern portion 15, and the workpiece 20 is grounded. Hence, a potential difference (or electric field) occurs between the pattern portion 15 and the workpiece 20. This electric field induces dielectric polarization in the imprint material 21 made of dielectric.

More specifically, negative charge occurs on the surface side of the imprint material 21 near the pattern portion 15 placed at the positive potential, and electrostatic attraction acts between the imprint material 21 and the pattern portion 15. By this electrostatic attraction, the imprint material 21 is attracted to the pattern portion 15. Consequently, even an ultrafine pattern depression (groove) in the range of ten to several ten nm is instantaneously filled up with the imprint material 21. Thus, all the pattern depressions can be filled up with the imprint material 21 within a pressing time of only 1 second.

Next, as shown in FIG. 3D, the template 10 is irradiated with ultraviolet radiation from above. The substrate 11 made of quartz and the conductive film 12 made of a DLC film are transparent to ultraviolet radiation. Hence, the ultraviolet radiation reaches the imprint material 21. For instance, by irradiation with ultraviolet radiation for approximately 1 second, the imprint material 21 is cured.

After the imprint material 21 is cured, the template holder 6 is moved up to strip the template 10 from the imprint material 21. Here, voltage application to the pattern portion 15 of the template 10 is stopped to eliminate the electrostatic attraction between the pattern portion 15 and the imprint material 21. Thus, the template 10 can be easily stripped from the imprint material 21.

Alternatively, immediately before stripping the template 10, as shown in FIG. 4A, a negative voltage, opposite to the positive voltage in the aforementioned pressing process, is applied to the pattern portion 15 for a short duration (such as 0.1 seconds). Thus, repulsion occurs between the pattern portion 15 and the imprint material 21, enabling the template 10 to be instantaneously stripped from the imprint material 21.

Migration of charge is slower in the imprint material 21 made of dielectric than in the conductive film 12. Thus, even if a negative potential is applied to the conductive film 12, or the surface of the pattern portion 15, positive charge does not immediately occur on the surface of the imprint material 21 opposed thereto, but for a certain period of time the polarization condition as shown in FIG. 3B is maintained. Hence, repulsion acts between the pattern portion 15 placed at the negative potential and the surface side of the imprint material 21 with negative charge occurring thereon. Thus, the pattern portion 15 can be instantaneously separated from the imprint material 21 without dragging the imprint material 21.

It was confirmed that by separating the pattern portion 15 from the imprint material 21 by producing repulsion between the pattern portion 15 and the imprint material 21 as described above, the number of demolding defects, in which the imprint material 21 is left in the pattern portion 15 particularly in its depression (groove), is reduced to approximately ⅕ of that in conventional techniques. Specifically, the number of demolding defects was approximately 0.2 defects/cm² in conventional techniques, but is reduced to 0.04 defects/cm² by using the method of this embodiment.

By stripping the template 10, as shown in FIG. 4B, a pattern of the cured imprint material 21 is formed on the workpiece 20. This pattern is a reverse pattern of the indentation pattern formed in the template 10. The patterned imprint material 21 is used as a mask to perform processing such as etching on the workpiece 20. Thus, as shown in FIG. 4C, an indentation pattern is formed in the workpiece 20.

The workpiece 20 is illustratively an insulating film, semiconductor film, or conductive film formed on a silicon or other substrate, or is a substrate itself. That is, the patterning method according to this embodiment corresponds to part of the processes in a method for manufacturing a semiconductor device.

Conventionally, in the process in which a template having a fine indentation pattern with a half-pitch of approximately 20 nm is pressed against an uncured imprint material, it takes approximately 10 seconds to gaplessly fill up the pattern depression with the imprint material. Furthermore, the template is slowly stripped from the imprint material, taking a time period of approximately 15 seconds to prevent demolding defects. Thus, a single pattern transfer requires nearly 30 seconds.

In contrast, in this embodiment in which a potential difference is produced between the pattern portion 15 and the workpiece 20, the pattern depression can be gaplessly filled up with the imprint material 21 even if the time period for pressing the pattern portion 15 against the uncured imprint material 21 is approximately 1 second, which is 1/10 of that in conventional techniques. Furthermore, immediately before the template 10 is stripped from the imprint material 21, an electric field opposite to that applied between the pattern portion 15 and the workpiece 20 during the pressing thereof is applied so that they can be instantaneously separated from each other without causing demolding defects.

Consequently, in this embodiment, a fine pattern with a half-pitch of approximately 20 nm can be formed by the imprint process in approximately 3 seconds. Thus, the throughput is improved, and the cost of manufacturing semiconductor devices can be significantly reduced. Furthermore, the number of defects can be reduced. This also serves to significantly reduce the cost of manufacturing semiconductor devices.

The timing of applying voltage to the conductive film 12 including the pattern portion 15 may be when the template 10 is moved close to the imprint material 21, or after the pattern portion 15 comes into contact with the imprint material 21. If the voltage starts to be applied to the conductive film 12 before the pattern portion 15 comes into contact with the imprint material 21, the imprint material 21 starts to be attracted to the pattern portion 15 immediately at the moment the pattern portion 15 comes into contact with the imprint material 21. Hence, the pressing time can be further reduced.

The aforementioned effect can be achieved as long as a potential difference is produced between the conductive film 12 and the workpiece 20 so that electrostatic attraction acts between the surface of the dielectrically polarized imprint material 21 and the pattern portion 15. Hence, the mode of voltage application is not limited to that in the above embodiment. It is also possible to ground the conductive film 12 and apply voltage to the workpiece 20, or to apply voltage to both the conductive film 12 and the workpiece 20.

If the potential difference between the conductive film 12 and the workpiece 20 is too small, the force attracting the imprint material 21 to the pattern portion 15 is weakened. Conversely, if it is too large, there is concern about defects and damage occurring in the pattern portion 15 due to discharge in the space (e.g., under atmospheric pressure) between the conductive film 12 and the workpiece 20. In view of these points, the potential difference produced between the conductive film 12 and the workpiece 20 is preferably in the range of 30 to 800 V. Setting to this potential difference range is also preferable when the voltage is applied immediately before the template 10 is stripped from the imprint material 21.

It is noted that while a voltage is applied to one of the conductive film 12 and the workpiece 20, the other may be left floating. However, the configuration of applying a positive or negative voltage to one of them and applying a voltage of opposite polarity to, or grounding, the other is superior in controllability within the desired potential difference (such as 30 to 800 V) because the potential difference occurring between the conductive film 12 and the workpiece 20 can be accurately controlled.

Starting and stopping the application of voltage to the conductive film 12 and the workpiece 20, and switching to the voltage of opposite polarity at the time of demolding, are performed under the control of the controller 1 shown in FIG. 1.

The conductive film 12 in which a fine indentation pattern is formed requires not only conductivity, but also mechanical strength and transparency to ultraviolet radiation. Materials satisfying this condition include ITO (indium tin oxide), indium oxide, and ruthenium oxide, besides DLC. Among them, DLC is superior in mechanical strength, and is more desirable in accurately transferring a fine pattern.

After the completion of fill-up of the pattern depression with the imprint material 21 by pressing the pattern portion 15 against the imprint material 21, the voltage application for producing the aforementioned potential difference may be stopped. However, even after the pressing process, if the aforementioned potential difference is produced to induce dielectric polarization in the imprint material 21 while the curing process and until immediately before stripping the template 10, the aforementioned repulsion can be produced between the surface of the imprint material 21 and the pattern portion 15 by switching the polarity of the voltage being applied to the conductive film 12 so that they can be instantaneously separated from each other.

To cure the imprint material, heat curing may also be used. However, heat curing causes concern about thermal expansion of the pattern. Hence, photocuring is preferable in applications requiring fine and accurate patterns such as semiconductor devices. 

1. A patterning method comprising: supplying an imprint material made of a dielectric in an uncured state onto a workpiece; producing a potential difference between the workpiece and a conductive pattern portion of a template opposed to the workpiece to induce dielectric polarization in the imprint material before curing the imprint material; bringing the pattern portion into contact with the imprint material in the uncured state; curing the imprint material with the pattern portion brought into contact with the imprint material; and stripping the template from the imprint material after curing the imprint material.
 2. The method according to claim 1, wherein the potential difference is produced between the workpiece and the pattern portion by applying a voltage to one of the workpiece and the pattern portion and grounding the other.
 3. The method according to claim 1, wherein the potential difference is produced between the workpiece and the pattern portion by applying a voltage to one of the workpiece and the pattern portion and applying a voltage of a second polarity opposite to a first polarity of the voltage applied to the one to the other.
 4. The method according to claim 1, wherein an electric field in a direction opposite to the electric field producing the potential difference is produced between the pattern portion and the workpiece immediately before the template is stripped from the imprint material.
 5. The method according to claim 4, wherein the potential difference produced is maintained until switching to the electric field in the opposite direction after the potential difference is produced between the workpiece and the pattern portion.
 6. The method according to claim 1, wherein the potential difference starts to be produced between the workpiece and the pattern portion before the pattern portion comes into contact with the imprint material.
 7. The method according to claim 1, wherein the template is stripped from the imprint material with the potential difference eliminated.
 8. The method according to claim 1, wherein the pattern portion is formed in a DLC (diamond-like carbon) film.
 9. The method according to claim 1, wherein the imprint material is an ultraviolet-curable resin, and the template is transparent to ultraviolet radiation.
 10. A patterning apparatus comprising: a workpiece holder capable of holding a workpiece; a template holder capable of holding a template including a conductive pattern portion; a contact probe connected to a power supply and being capable of moving relative to the pattern portion to come into contact therewith; a moving mechanism configured to cause the workpiece holder and the template holder to move close to each other to bring the pattern portion into contact with an imprint material made of a dielectric in an uncured state supplied onto the workpiece, and to cause the workpiece holder and the template holder to move away from each other after the imprint material is cured; and a controller configured to apply a voltage to the pattern portion through the contact probe in contact with the pattern portion before the imprint material is cured.
 11. The apparatus according to claim 10, wherein after the imprint material is cured and immediately before the template is stripped from the imprint material, the controller applies a voltage of a second polarity opposite to a first polarity of the voltage applied before the imprint material is cured to the pattern portion through the contact probe.
 12. A method for manufacturing a semiconductor device, comprising: supplying an imprint material made of a dielectric in an uncured state onto a workpiece; producing a potential difference between the workpiece and a conductive pattern portion of a template opposed to the workpiece to induce dielectric polarization in the imprint material before curing the imprint material; bringing the pattern portion into contact with the imprint material in the uncured state; curing the imprint material with the pattern portion brought into contact with the imprint material; stripping the template from the imprint material after curing the imprint material; and processing the workpiece by using the imprint material from which the template has been stripped as a mask.
 13. The method according to claim 12, wherein the potential difference is produced between the workpiece and the pattern portion by applying a voltage to one of the workpiece and the pattern portion and grounding the other.
 14. The method according to claim 12, wherein the potential difference is produced between the workpiece and the pattern portion by applying a voltage to one of the workpiece and the pattern portion and applying a voltage of a second polarity opposite to a first polarity of the voltage applied to the one to the other.
 15. The method according to claim 12, wherein an electric field in a direction opposite to the electric field producing the potential difference is produced between the pattern portion and the workpiece immediately before the template is stripped from the imprint material.
 16. The method according to claim 15, wherein the potential difference produced is maintained until switching to the electric field in the opposite direction after the potential difference is produced between the workpiece and the pattern portion.
 17. The method according to claim 12, wherein the potential difference starts to be produced between the workpiece and the pattern portion before the pattern portion comes into contact with the imprint material.
 18. The method according to claim 12, wherein the template is stripped from the imprint material with the potential difference eliminated.
 19. The method according to claim 12, wherein the pattern portion is formed in a DLC (diamond-like carbon) film.
 20. The method according to claim 12, wherein the imprint material is an ultraviolet-curable resin, and the template is transparent to ultraviolet radiation. 